| Message ID | 20221111183532.3676646-27-kristen@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add Cgroup support for SGX EPC memory | expand |
On 11/12/22 01:35, Kristen Carlson Accardi wrote: > diff --git a/Documentation/x86/sgx.rst b/Documentation/x86/sgx.rst > index 2bcbffacbed5..f6ca5594dcf2 100644 > --- a/Documentation/x86/sgx.rst > +++ b/Documentation/x86/sgx.rst > @@ -300,3 +300,80 @@ to expected failures and handle them as follows: > first call. It indicates a bug in the kernel or the userspace client > if any of the second round of ``SGX_IOC_VEPC_REMOVE_ALL`` calls has > a return code other than 0. > + > + > +Cgroup Support > +============== > + > +The "sgx_epc" resource within the Miscellaneous cgroup controller regulates > +distribution of SGX EPC memory, which is a subset of system RAM that > +is used to provide SGX-enabled applications with protected memory, > +and is otherwise inaccessible, i.e. shows up as reserved in > +/proc/iomem and cannot be read/written outside of an SGX enclave. > + > +Although current systems implement EPC by stealing memory from RAM, > +for all intents and purposes the EPC is independent from normal system > +memory, e.g. must be reserved at boot from RAM and cannot be converted > +between EPC and normal memory while the system is running. The EPC is > +managed by the SGX subsystem and is not accounted by the memory > +controller. Note that this is true only for EPC memory itself, i.e. > +normal memory allocations related to SGX and EPC memory, e.g. the > +backing memory for evicted EPC pages, are accounted, limited and > +protected by the memory controller. > + > +Much like normal system memory, EPC memory can be overcommitted via > +virtual memory techniques and pages can be swapped out of the EPC > +to their backing store (normal system memory allocated via shmem). > +The SGX EPC subsystem is analogous to the memory subsytem, and > +it implements limit and protection models for EPC memory. > + > +SGX EPC Interface Files > +----------------------- > + > +For a generic description of the Miscellaneous controller interface > +files, please see Documentation/admin-guide/cgroup-v2.rst > + > +All SGX EPC memory amounts are in bytes unless explicitly stated > +otherwise. If a value which is not PAGE_SIZE aligned is written, > +the actual value used by the controller will be rounded down to > +the closest PAGE_SIZE multiple. > + > + misc.capacity > + A read-only flat-keyed file shown only in the root cgroup. > + The sgx_epc resource will show the total amount of EPC > + memory available on the platform. > + > + misc.current > + A read-only flat-keyed file shown in the non-root cgroups. > + The sgx_epc resource will show the current active EPC memory > + usage of the cgroup and its descendants. EPC pages that are > + swapped out to backing RAM are not included in the current count. > + > + misc.max > + A read-write single value file which exists on non-root > + cgroups. The sgx_epc resource will show the EPC usage > + hard limit. The default is "max". > + > + If a cgroup's EPC usage reaches this limit, EPC allocations, > + e.g. for page fault handling, will be blocked until EPC can > + be reclaimed from the cgroup. If EPC cannot be reclaimed in > + a timely manner, reclaim will be forced, e.g. by ignoring LRU. > + > + misc.events > + A read-write flat-keyed file which exists on non-root cgroups. > + Writes to the file reset the event counters to zero. A value > + change in this file generates a file modified event. > + > + max > + The number of times the cgroup has triggered a reclaim > + due to its EPC usage approaching (or exceeding) its max > + EPC boundary. > + > +Migration > +--------- > + > +Once an EPC page is charged to a cgroup (during allocation), it > +remains charged to the original cgroup until the page is released > +or reclaimed. Migrating a process to a different cgroup doesn't > +move the EPC charges that it incurred while in the previous cgroup > +to its new cgroup. The doc LGTM, thanks. Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
diff --git a/Documentation/x86/sgx.rst b/Documentation/x86/sgx.rst index 2bcbffacbed5..f6ca5594dcf2 100644 --- a/Documentation/x86/sgx.rst +++ b/Documentation/x86/sgx.rst @@ -300,3 +300,80 @@ to expected failures and handle them as follows: first call. It indicates a bug in the kernel or the userspace client if any of the second round of ``SGX_IOC_VEPC_REMOVE_ALL`` calls has a return code other than 0. + + +Cgroup Support +============== + +The "sgx_epc" resource within the Miscellaneous cgroup controller regulates +distribution of SGX EPC memory, which is a subset of system RAM that +is used to provide SGX-enabled applications with protected memory, +and is otherwise inaccessible, i.e. shows up as reserved in +/proc/iomem and cannot be read/written outside of an SGX enclave. + +Although current systems implement EPC by stealing memory from RAM, +for all intents and purposes the EPC is independent from normal system +memory, e.g. must be reserved at boot from RAM and cannot be converted +between EPC and normal memory while the system is running. The EPC is +managed by the SGX subsystem and is not accounted by the memory +controller. Note that this is true only for EPC memory itself, i.e. +normal memory allocations related to SGX and EPC memory, e.g. the +backing memory for evicted EPC pages, are accounted, limited and +protected by the memory controller. + +Much like normal system memory, EPC memory can be overcommitted via +virtual memory techniques and pages can be swapped out of the EPC +to their backing store (normal system memory allocated via shmem). +The SGX EPC subsystem is analogous to the memory subsytem, and +it implements limit and protection models for EPC memory. + +SGX EPC Interface Files +----------------------- + +For a generic description of the Miscellaneous controller interface +files, please see Documentation/admin-guide/cgroup-v2.rst + +All SGX EPC memory amounts are in bytes unless explicitly stated +otherwise. If a value which is not PAGE_SIZE aligned is written, +the actual value used by the controller will be rounded down to +the closest PAGE_SIZE multiple. + + misc.capacity + A read-only flat-keyed file shown only in the root cgroup. + The sgx_epc resource will show the total amount of EPC + memory available on the platform. + + misc.current + A read-only flat-keyed file shown in the non-root cgroups. + The sgx_epc resource will show the current active EPC memory + usage of the cgroup and its descendants. EPC pages that are + swapped out to backing RAM are not included in the current count. + + misc.max + A read-write single value file which exists on non-root + cgroups. The sgx_epc resource will show the EPC usage + hard limit. The default is "max". + + If a cgroup's EPC usage reaches this limit, EPC allocations, + e.g. for page fault handling, will be blocked until EPC can + be reclaimed from the cgroup. If EPC cannot be reclaimed in + a timely manner, reclaim will be forced, e.g. by ignoring LRU. + + misc.events + A read-write flat-keyed file which exists on non-root cgroups. + Writes to the file reset the event counters to zero. A value + change in this file generates a file modified event. + + max + The number of times the cgroup has triggered a reclaim + due to its EPC usage approaching (or exceeding) its max + EPC boundary. + +Migration +--------- + +Once an EPC page is charged to a cgroup (during allocation), it +remains charged to the original cgroup until the page is released +or reclaimed. Migrating a process to a different cgroup doesn't +move the EPC charges that it incurred while in the previous cgroup +to its new cgroup.